Polyurethane foam for heat insulation material, and refrigerator

Abstract

To provide polyurethane foam for a heat insulation material having excellent heat insulation properties and strength, and provide a refrigerator having heat insulation properties for a prolonged period.SOLUTION: A refrigerator 10 includes a polyurethane foam 40 for a heat insulation material which includes polyurethane foam and aerogel distributed in the polyurethane foam. An average particle diameter D50 of the aerogel is in a range between 10 μm or more and 100 μm or less.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to polyurethane foam for heat insulation materials and refrigerators.

Background Art

[0002] It has been considered to use an aerogel-containing polyurethane foam in which aerogel is dispersed in polyurethane foam as a heat insulation material for refrigerators (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There is a desire for further improvement in the heat insulation performance of the polyurethane foam used as a heat insulation material. In addition, for the heat insulation material used in a refrigerator, it is desired to have high strength so as not to be damaged even when receiving impacts due to opening and closing of the door over a long period of time.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a polyurethane foam for a heat insulation material excellent in heat insulation performance and strength, and a refrigerator having excellent heat insulation performance over a long period of time.

Means for Solving the Problems

[0006] In order to solve the above problems, the present inventors have found that it is effective to disperse fine aerogel in polyurethane foam, and have completed the present invention. Therefore, the present invention provides the following.

[0007] (1) A polyurethane foam for heat insulation, comprising a polyurethane foam and an aerogel dispersed in the polyurethane foam, wherein an average particle diameter D50 of the aerogel is in a range of 10 μm or more and 100 μm or less.

[0008] According to the polyurethane foam for heat insulation of (1), by using a fine aerogel having an average particle diameter D50 of the aerogel within the above range, the foam breakage of cells during the production of the polyurethane foam is suppressed, the foam breakage rate is reduced, and the generation of coarse cells is suppressed, resulting in a smaller average cell diameter of the cells. Therefore, the polyurethane foam for heat insulation of the present embodiment is excellent in heat insulation properties and strength.

[0009] (2) The polyurethane foam for heat insulation according to (1) above, wherein a particle diameter D90 of 90 volume% of the integrated value in the particle size distribution of the aerogel is in a range of 40 μm or more and 150 μm or less.

[0010] According to the polyurethane foam for heat insulation of (2), since the particle diameter D90 of the aerogel is within the above range and the content of coarse aerogel is small, the cells of the polyurethane foam are less likely to break.

[0011] (3) The polyurethane foam for heat insulation according to (1) or (2) above, wherein a content rate of the aerogel is in a range of 0.1 mass% or more and 0.3 mass% or less.

[0012] According to the polyurethane foam for heat insulation of (3), since the content rate of the aerogel is within the above range, the heat conductivity and strength are further improved.

[0013] (4) A refrigerator comprising the polyurethane foam for heat insulation according to any one of (1) to (3) above.

[0014] According to the refrigerator of (4), since it is provided with the above-described polyurethane foam for heat insulation, it has excellent heat insulation properties over a long period of time.

Effects of the Invention

[0015] According to the present invention, it is possible to provide a polyurethane foam for a heat insulating material excellent in heat insulation and strength, and a refrigerator having excellent heat insulation over a long period of time.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0017] Hereinafter, a polyurethane foam for a heat insulating material and a refrigerator according to an embodiment of the present invention will be described.

[0018] The polyurethane foam for a heat insulating material of the present embodiment includes a polyurethane foam and an aerogel dispersed in the polyurethane foam. As the aerogel, silica aerogel can be used.

[0019] The polyurethane foam is a rigid polyurethane foam and has independent cells (closed cells). The average cell diameter of the cells of the polyurethane foam is, for example, in the range of 100 μm or more and 200 μm or less.

[0020] In the present embodiment, the average particle diameter D50 of the aerogel is in the range of 10 μm or more and 100 μm or less. By using a fine aerogel in which the average particle diameter D50 of the aerogel is within the above range, the cell collapse during the production of the polyurethane foam is suppressed, the collapse rate is reduced, and the generation of coarse cells is suppressed, so that the average cell diameter of the cells becomes small. Therefore, the polyurethane foam for a heat insulating material of the present embodiment is excellent in heat insulation and strength.

[0021] The particle size D90 of the integrated value of 90% by volume in the particle size distribution of the aerogel may be, for example, in the range of 40 μm or more and 150 μm or less. When the particle size D90 is within the above range and the content of the coarse aerogel is small, the cells of the polyurethane foam are less likely to collapse. The particle size D10 of the integrated value of 10% by volume in the particle size distribution of the aerogel may be, for example, in the range of 5 μm or more and 30 μm or less.

[0022] The ratio D50 / D90 of the average particle size D50 to the particle size D90 may be, for example, 0.07 or more, or may be 0.3 or more. The ratio D50 / D10 of the average particle size D50 to the particle size D10 may be, for example, 1.5 or more, or may be in the range of 1.5 or more and 3.0 or less. The particle size distribution of the aerogel is a value measured by the laser diffraction scattering method.

[0023] The content of the aerogel may be, for example, in the range of 0.1% by mass or more and 3% by mass or less. When the content of the aerogel is within the above range, the heat insulation and strength are further improved.

[0024] The polyurethane foam for heat insulation material of the present embodiment can be obtained, for example, by mixing each raw material such as a polyol compound, an isocyanate compound, a foaming agent, an aerogel, and a catalyst, reacting the polyol compound and the isocyanate compound, and foaming the produced aerogel-containing polyurethane foam. As a method for mixing the raw materials of the polyurethane foam for heat insulation material, a method may be used in which a mixed liquid containing a polyol compound, a foaming agent, an aerogel, and a catalyst is used as the first liquid, a liquid isocyanate compound is used as the second liquid, and the first liquid and the second liquid are mixed. The viscosity of the first liquid may be in the range of 400 Pa·s or more and 750 Pa·s or less, and the viscosity of the second liquid may be in the range of 200 Pa·s or more and 400 Pa·s or less. When the viscosity of the first liquid and the viscosity of the second liquid are within the above range, a mixed liquid with a uniform composition is likely to be generated when the first liquid and the second liquid are mixed. The viscosity is a value measured at a liquid temperature of 20°C using a B-type rotational viscometer.

[0025] As the polyol compound, amine-based polyols and polyester-based polyols can be used. As the amine-based polyols, triethanolamine, ethylenediamine, aromatic diamines, and diethylenetriamine can be mentioned. The polyester-based polyols are produced by dehydrative condensation of several kinds of carboxylic acids and polyhydric alcohols. As the carboxylic acids, adipic acid, phthalic acid, etc. can be used. As the polyhydric alcohols, ethylene glycol, 1,4-butanediol, 1,6-hexanediol, etc. can be used. The polyol compound may be used alone or in combination of two or more kinds.

[0026] As the isocyanate compound, toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and xylene diisocyanate can be used. These isocyanate compounds may be used alone or in combination of two or more kinds.

[0027] As the foaming agent, cyclopentane, trichlorofluoromethane, 1,1-dichloro-1-fluoromethane, 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, and carbon dioxide can be used. These foaming agents may be used alone or in combination of two or more kinds.

[0028] The catalyst is used to adjust the reaction rate between the polyol compound and the isocyanate compound. As the catalyst, aliphatic amines can be used. Examples of the aliphatic amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, triethanolamine, N,N-diisopropylethylamine, tetramethylethylenediamine, hexamethylenediamine, spermidine, spermine, amantadine, tetramethylhexanediamine, and pentamethyldiethylenetriamine. The catalyst may be used alone or in combination of two or more kinds.

[0029] As the polyol compound, a polyol mixture in which a polyol compound and a catalyst are previously mixed may be used.

[0030] Next, the refrigerator of the present embodiment will be described. FIG. 1 is a front view showing a refrigerator according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1.

[0031] As shown in FIGS. 1 and 2, the refrigerator 10 of the present embodiment has a structure partitioned into three stages: an upper stage portion 11, a middle stage portion 12, and a lower stage portion 13. The refrigerator 10 includes a heat-insulating box body 30 with an open front and a door for opening and closing the opening of the heat-insulating box body. The upper stage portion 11 can be opened and closed by an upper right heat-insulating door 21a and an upper left heat-insulating door 21b, the middle stage portion 12 can be opened and closed by a middle heat-insulating door 22, and the lower stage portion 13 can be opened and closed by a lower heat-insulating door 23. The upper right heat-insulating door 21a is a rotary door that can rotate about the right side end surface, and the upper left heat-insulating door 21b is a rotary door that can rotate about the left end portion. The middle heat-insulating door 22 and the lower heat-insulating door 23 are each a drawer-type door provided with a storage container 24.

[0032] As shown in FIG. 2, the heat-insulating box body 30 has a polyurethane foam 40 for heat insulation and a frame 50 that covers the outside of the polyurethane foam 40 for heat insulation. The polyurethane foam 40 for heat insulation is the polyurethane foam for heat insulation of the above-described present embodiment.

[0033] As shown in FIG. 2, a machine room 61 is provided on the back side of the lower stage portion 13 of the refrigerator 10. A compressor 62 is housed in the machine room 61. A cooling chamber 63 is partitioned and formed on the back side of the middle stage portion 12, and an evaporator 64 is housed in the cooling chamber 63. The evaporator 64 and the compressor 62 are connected via an expansion means and a condenser (not shown) and a refrigerant pipe to form a vapor compression refrigeration cycle.

[0034] Part of the cold air inside the cooling chamber 63 cooled by the evaporator 64 is sent to the middle section 12 through the blower 65 and the cold air pipe 66 to cool the middle section 12. The cold air that has cooled the middle section 12 flows into the cooling chamber 63 and is cooled again by the evaporator 64. The remaining cold air is sent to the upper section 11 to cool the upper section 11. The cold air that has cooled the upper section 11 is sent to the lower section 13 through a cold air pipe (not shown). After cooling the lower section 13, it is sent to the cooling chamber 63 through a cold air pipe (not shown) and is cooled again by the evaporator 64. A damper (not shown) is arranged in the cold air pipe. The control device (not shown) of the refrigerator 10 controls the opening and closing of the damper based on the temperature inside the refrigerator measured by an in-box temperature sensor (not shown). Thereby, the flow rate of the cold air is adjusted to keep the temperature inside the refrigerator constant. In this way, the upper section 11, the middle section 12, and the lower section 13 are cooled to a predetermined temperature range. The arrows in Fig. 2 indicate the flow of the cold air. Further, below the evaporator 64, a defrosting heater 67 for melting the frost on the evaporator 64 is provided.

[0035] Since the heat insulation box body 30 of the refrigerator 10 configured as described above includes the polyurethane foam 40 for heat insulation material, it has excellent heat insulation performance over a long period.

[0036] As described above, the embodiments of the present invention have been described in detail, but the present invention is not limited to the above embodiments.

Example

[0037] [Example 1] 100 parts by mass of a polyol mixture containing a catalyst (manufactured by Sumika Covestro Urethane Co., Ltd.), 14 parts by mass of a blowing agent (cyclopentane), and 0.25 parts by mass of an aerogel (particle size D10: 11.8 μm, particle size D50 (average particle size): 20.0 μm, particle size D90: 48.0 μm) were mixed to prepare a first liquid. As a result of measuring the viscosity of the first liquid (liquid temperature: 20 °C) using a B-type rotational viscometer (manufactured by Toki Sangyo Co., Ltd., TVC-10 type viscometer, using rotor NO. 24), it was 562 Pa·s.

[0038] Liquid diphenylmethane diisocyanate was prepared as the second liquid. The viscosity of the second liquid (liquid temperature: 20°C) was measured using a B-type rotational viscometer (manufactured by Toki Sangyo Co., Ltd., TVC-10 viscometer, using rotor NO. 24), and the result was 322 Pa·s.

[0039] 114.25 parts by mass of the first liquid (liquid temperature: 20°C) and 124 parts by mass of the second liquid (liquid temperature: 20°C) were mixed and stirred under the conditions of a stirring speed of 4000 rpm for 4 seconds. The resulting mixed liquid was poured into a jig, and reacted and foamed under the conditions of a jig temperature of 40°C and a curing time of 10 minutes to produce a polyurethane foam.

[0040] [Example 2, Comparative Example 1] As the aerogel, a first liquid was prepared in the same manner as in Example 1, except that an aerogel having the particle size distribution described in Table 1 below was used. The viscosity of the obtained first liquid is shown in Table 1 below. A polyurethane foam was produced in the same manner as in Example 1, except that the obtained first liquid was used.

[0041]

Table 1

[0042] [Evaluation] For the polyurethane foams obtained in Examples 1 to 2 and Comparative Example 1, the density, average cell diameter, bubble breakage rate, thermal conductivity, and compressive strength at 10% deformation were measured by the following methods. The results are shown in Table 2 below.

[0043] (Density) The obtained heat insulating material was cut into a square shape in plan view to obtain a test piece. The size of the obtained test piece was measured with calipers to calculate the volume of the test piece, and the weight of the test piece was measured with an analytical balance. The density was obtained by dividing the weight of the test piece by the volume.

[0044] (Average cell diameter) The polyurethane foam was cut perpendicular to the foaming direction, and the cut surface of the obtained polyurethane foam was observed using a microscope. Cells (closed cells) with a major axis of 10 μm or more were extracted. The major axis of the extracted cells was measured, and the average was taken as the average cell diameter. The measurement of the major axis was performed on 30 or more cells.

[0045] (Foam breakage rate) The open-cell ratio and closed-cell ratio of the polyurethane foam were measured using a dry-type automatic densitometer, AccuPyc 1330 (manufactured by Shimadzu Corporation). The foam breakage rate was calculated from the open-cell ratio and closed-cell ratio as follows, considering the open cells as broken cells. Foam breakage rate (%) = Open-cell ratio (%) / {Open-cell ratio (%) + Closed-cell ratio (%)}

[0046] (Thermal conductivity) The thermal conductivity in the thickness direction of the polyurethane foam was measured using a thermal conductivity measuring device (FOX200, manufactured by Eihong Seiki Co., Ltd.).

[0047] (Compressive strength at 10% deformation) The compressive strength in the thickness direction of the polyurethane foam was measured using a tensile testing machine (manufactured by A&D). The test condition was a compressive strength of 5 mm / min, and the value at 10% deformation was calculated as follows. Compressive strength at 10% deformation (kgf / cm 2 ) = Load at 10% deformation (kg) / Compressive surface area of the test piece before compression (cm 2 )

[0048]

Table 2

[0049] From the results in Table 1 and Table 2, it can be seen that the polyurethane foams of Examples 1 and 2, where the average particle diameter D50 of the aerogel is within the scope of the present invention, have the same density as the polyurethane foam of Comparative Example 1 where the average particle diameter D50 of the aerogel exceeds the scope of the present invention. However, the average cell diameter and the cell opening ratio are lower, the thermal conductivity is lower and the heat insulation property is higher, and the compression strength is higher. In Examples 1 and 2, during the production of the polyurethane foam, the foaming of the polyurethane by the aerogel is less likely to be inhibited, the cell opening is suppressed, the cell opening ratio is reduced, and the generation of coarse cells is suppressed. For this reason, it is considered that the average cell diameter of the polyurethane foam is small, and the heat insulation property and strength are improved. On the contrary, in Comparative Example 1, during the production of the polyurethane foam, the foaming of the polyurethane is inhibited by the aerogel, the cells are opened, and the generation of coarse cells is likely to occur. For this reason, it is considered that the average cell diameter of the polyurethane foam is large, and the heat insulation property and strength are reduced.

Explanation of symbols

[0050] 10 Refrigerator 11 Upper part 12 Middle part 13 Lower part 21a Upper right heat-insulating door 21b Upper left heat-insulating door 22 Middle heat-insulating door 23 Lower heat-insulating door 24 Storage container 30 Heat-insulating box body 40 Polyurethane foam for heat-insulating material 50 Frame 61 Machine room 62 Compressor 63 Cooling chamber 64 Evaporator 65 Blower 66 Cold air pipe 67 Defrosting heater

Claims

1. A polyurethane foam and an aerogel dispersed in the polyurethane foam, The polyurethane foam for heat insulation, wherein the average particle diameter D50 of the aerogel is in the range of 10 μm or more and 100 μm or less.

2. The polyurethane foam for heat insulation according to claim 1, wherein the particle diameter D90 of 90% by volume of the integrated value in the particle size distribution of the aerogel is in the range of 40 μm or more and 150 μm or less.

3. The polyurethane foam for heat insulation according to claim 1 or 2, wherein the content of the aerogel is in the range of 0.1% by mass or more and 3% by mass or less.

4. A refrigerator comprising the polyurethane foam for heat insulation according to claim 1 or 2.

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